Is there any Successful website developed by cshtml5? How does it compare to html5?(I mean performance and other things. does it have overheads or not). what I want to conclude from these questions is that Can I rely on this and give up on learning html,css,javascript&...

Yes, large applications can be built with this program, but I don't have anything public facing that I can share yet.

NO, DO NOT STOP LEARNING JavaScript, CSS and HTML! Continue to learn these for as long as you are developing web applications!

Why? Because understanding these technologies will only help you design better, faster, and more stable applications using this compiler (CSHTML5), as well as writing your own raw code. It will also help you debug and troubleshoot issues in your compiled CSHTML5 applications, and provides you the knowledge to develop extensions for CSHTML5 based on existing JS and CSS libraries.